Process for preparing organic disulfides



United States Patent 3 Claims. (Cl. 26079) ABSTRACT OF THE DISCLOSURE Aprocess for preparing a polymeric organic disulfide by the reaction ofan alkali metal tetrathiocarbonate with an organic halide. The polymersare useful in coating, impregnating, sealing and caulking compositions.

This is a division of application Ser. No. 436,687, filed Mar. 2, 1965,now Patent No. 3,367,975. The invention relates to a process forpreparing organic disulfides by the reaction of an alkali metaltetrathiocarbonate with an organic halide. The resulting disulfidereaction products are monomeric or polymeric compounds depending onwhether the organic halide used is mono-functional or poly-functional.

In accordance with the present invention, an organic halide is mixedwith a stoichiometric proportion of an alkali metal tetrathiocarbonatein a lower aliphatic alcohol reaction medium, and the mixture is heatedat refluxing temperature for a period sufficient to bring about thedesired reaction as illustrated below, usually a period between about 30minutes and about 48 hours.

wherein M is an alkali metal, R is an organic radical, X is a halogenselected from the group consisting of chlorine and bromine, and n is aninteger from 1 to 3 inclusive.

Any organic halide that will react with the alkali metaltetrathiocarbonate at the reflux temperature of the alcohol solution maybe employed provided that the halide is not so volatile that it mayescape from the reaction mixure as a gas before reacting, and providedthat it does not undergo simultaneous secondary or side reactions. Inpractice, I prefer to employ mono-, di-, and trifunctional primary andsecondary aliphatic chlorides and bromides of 1 to 20 carbon atomscontaining in addition to the chlorine substituents only aliphatichydrocarbon, or ether, or acetal groups.

Especially useful monofunctional halides are the primary aliphaticbromides and chlorides of the general formula RICHZX wherein R is analiphatic hydrocarbon group of 1 to 20 carbon atoms and X is chlorine orbromine. Illustrative of this group there may be mentioned ethylbromide, ethyl chloride, propyl chloride and bromide, butyl chloride andbromide, pentyl chloride and bromide, and the hexyl, heptyl, octyl,decyl and up to dodecyl chloride and bromide.

Monofunctional secondary aliphatic bromides and chlorides containing 3to 20 carbon atoms inclusive are also especially useful, for example,2-bromopropane, 2-bromobutane, 2-bromooctane, 2-bromodecane, up to2-bromododecane and the corresponding chlorides, 2-chloropropane,2-chlorobutane, 2-chlorooctane, 2-chlorooctadecane, 2-chlorododecane, aswell as the isomeric secondary aliphatic 3-20 carbon atoms chlorides andbromides, in which the halogen atom is attached to other than the secice0nd atom of the hydrocarbon chain such as 3-chlorooctane, 4-bromooctane,and so on.

Suitable diand trifunctional halides include the 120 carbon atomaliphatic dibromides and dichlorides, for example, bis(2-chloroethyl)ether, bis(2-bromoethyl) ether,"

bis(2-chloroethyl) formal, bis(2-bromoethyl) formal, bis- (chloropropyl)formal, bis(bromobutyl) formal, bis(chloropentyl) formal, ethylenedichloride, ethylene dibromide, propylene dichloride, propylenedibromide, 1,2,3-trichloropropane, 1,2,3-tribromopropane,trichlorobutane, trichloro'pentane, and the like.

My preferred diand trifunctional reactants are bis(2- chloroethyl)formal, bis(Z-bromoethyl) formal, bis-(2- chloroethyl) ether,bis(2-bromoethyl) ether, 1,2,3-trichloropropane and1,2,3-tribromopropane.

When the organic halide is monofunctional, the resulting reactionproduct is a simple monomeric compound. Thus such halides as methylchloride or bromide, ethyl chloride or bromide, propyl chloride orbromide, butyl chloride or bromide, etc., result in the production ofthe monomeric disulfides:

action products are polymeric compounds and form repeating units of thecharacter:

F I I" I RS-S Ll l L J E l Polymer from Polymer from difunctional halidetrifunctional halide The reactions indicated above are unexpected inthat the disulfide linkage is introduced into the polymeric unit ratherthan a tetrathiocarbonate unit. The process of my invention thereforeprovides a novel means for introducing the disulfide linkage intoorganic polymers of this character.

In accordance with a specific embodiment of the present invention, soliddisulfide polymers are prepared by the reaction of bis(2-haloethyl)formal with an alkali metal tetrathiocarbonate in substantiallystoichiometric proportions, with or without the inclusion of smallproportions of trichloropropane as cross linking agent, thus producing asolid, acetone-insoluble polymer. The solid polymer can then beliquefied, as by reaction with sodium hydrosulfide, and the.liquidpolymer resolidified in final use with an oxidizing agent such as leaddioxide.

.The reaction according to my invention proceeds as indicated below:

sodium tetradihaloethyl thioearbonate formal CzH4OCH2OC2H4S-S 2 NaX CS;

disulfide polymer wherein X represents chlorine or bromine.

In carrying out the prepartion of the disulfide polymers of myinvention, the alkali metal tetrathiocarbonate (e.g., Na CS and adifunctional halide such as dichloroor dibromoethyl formal are mixed anddispersed in a lower aliphatic alcohol reaction medium in substantiallystoichiometric proportions. Methyl, ethyl, propyl, and

, 3 4 I butyl alcohols are especially suitable, ethyl alcohol beingPolysulfide sealants are prepared by compounding the preferred. Ifdesired, small proportions of trifunctional liquefied polymers withcuring agents, fillers, plasticizers, halide cross linking agent such astrichloropropane may adhesion promotors and other agents to form amastic. be substituted for a small part of the difunctional dihalo-Curing agents'are used to accelerate or retard the conethyl formal toincrease the viscosity of the resulting 5 version of the liquid polymersto cross linked solids. polymer, but this is not necessary for theproduction of Metallic oxides, metallic peroxides, organic peroxides, asolid elastic polymer. The resulting mixture is then and organic nitrocompounds are examples of accelerheated conveniently at or below thereflux temperature of ators that can be used. Stearic and oleic acid canbe used the mixture, for example, between about 40C. and about asretarders. Fillers can be used to improve the physical 100 C., andmaintained at these temperatures until poproperties of the curedpolymers. Suitable fillers are lymerization is complete, usually in aperiod not more carbon black, calcium carbonate, colloidal silica,titanium than about 50 hours, usually between about 10 hours anddioxide, lithopone, zinc sulfide, and the like. Plasticizers about 30hours. In general, it is preferred to blanket the can be used whensofter cured polymers are required. reactants 'with nitrogen or otherinert gas to avoid pre- Dibutyl phthalate and other dibasic acid estersare satismature oxidation of the product. factory. Liquid epoxy andphenolic resins can be added Proportions of reactants will preferably bein the molar to P mote d e and ful'an ,re nS and chlorinated ratio ofalkali metal tetrathiocarbonate to dihaloethyl rubb an be sed asprimers. formal to trichlorop'ropane between 1:1:00 to 110.85 20.10. Thealkali metal tetfathioeafbonate used as Starting The resulting polymerproduct may be a mixture of mat rial is readily prepared by reaction ofan alkali solid and liquid oly er whi h can be separated f o metalhydrosulfide with sulfur and carbon disulfide in each other bysuccessive extraction with ethyl alcohol alcoholic solution according tohe s m and acetone. h) a The solid polymers thus produced can beliquefied in 2Na SH S +CS2 Nazcs'i HZST the manner known in theliquefaction of conventional e fOhOWlhg speelhe examples furtherillustrate th polysulfide polymers as b treatment i h a cleavageinvention. Parts are by weight except as otherwise noted. agent, such assodium hydrosulfide (NaHS) or mixture EXAMPLE 1 of sodium hydrosulfideand sodium sulfite to break the polymer molecules at the -SS link andgenerate Preparetloh of P y mereapto groups as illustrated below! Sixpolymer preparations were carried out, in the first of which 237 grams(0.127 mole) of sodium tetrathio- R SN HSR N S O carbonate were mixedwith 22.0 grams (0.127 mole) of a2 2 3 bis (2-chloroethyl) formal and200 ml. of absolute ethyl The resulting liquefied P y are capable ofbeing alcohol. In the remaining preparations, various propor- Chl'ed atmom temperature (e elevated tions of the dichloroethyl formal werereplaced by tritempefathl'es to rubber-like er and 'f e usefulchloropropane. The mixtures were heated and stirred at in a vari ty ofapplieatlohs, ihelhdlhlg chafing and lmpreg' reflux of 78 C. undernitrogen for 24 hours, then allowed nating compositions and in sealingand caulking materials, to Stand at 25 fo 16 hours Particularly for usein Sealing ehTtaih e expfihsioh In each case, the product was a yellowliquid phase l y are (1150 hsefh1 in the Prepare/[10h of and a solidphase consisting of a yellow gummy solid larly shaped rubber-likearticles which can conveniently 40 mixed with a powdery yellow solid Theliquid phase was e made from the liquefied Polymers castlhg then} mdecanted from the solid, and the solid was washed with Sultahle moldsend curing them to Preduce the deslred four 50-ml. portions of alcoholthen with four 50-ml. porh amcletions of acetone. The solids were driedand weighed and The hquld merehpto tgrmmatedpolvmets can e cured thenWashed with water to dissolve the salt formed as a by Oxidation to thedlsulfide wlth a vanety of by-product in the reaction, and the insolubleresidue was oxidizing agehtsagain dried and weighed. The alcoholsolutions and the [0] alcohol washings were combined and evaporated, andthe RSH HER- R S S R H2O residues weighed. The acetone soluble fractionswere simy of the Conventional OXidiZihg agents y ilarly recovered andweighed after evaporation of the ployed, such as air, oxygen, all c idesand peroxacetone. In each case, the weight of the water soluble ides, asWell as Oxygen-containing Salts Such as ehfomates, fraction was in therange of 95-105 of the theoretical manganates, and permanganates. Whenthe liquid polyweight of the sodium chloride produced in the reaction.mer is to be used as a coating or as an impregnant f r The theoreticalyields and characteristics of the various porous materials such aspaper, leather, or the like, curing polymer fractions are listed inTable I.

TABLE I.POLYMERS PREPARED WITH DICHLOROE'IHYL FORMAL AND SODIUMTETRATHIOCARBONATE Percentage Yield of polymer iractions, TotalViscosity of polymer fractions Polymer number of formal percent 1 yieldof replaced by Molal ratio polymer,

trichloro- Alcohol Acetone Insoluble percent Alcohol Acetone Insolublepropane soluble soluble soluble soluble 0 1. 0:1. 0:00 25 15 100 Thinliquid. Thin liquid Plastic solid. 7. 5 1. 0:0. 85:0. 10 15 15 95 do doElastic solid. 0. 8 1. 0:0. 997:.002 20 50 10 Sticky, plastic solid. 0.320 20 55 95 Elastic solid. 1.5 15 40 30 do do Plastic soldi. 1. 5 25 2055 100 do Very viscous oil-.- Sticky, plastic solid.

1 Sodium tctrathiocarbonate: dichloroethyl formal: trichloropropane. 2Polymer yield calculated as percent of theory for a disulfide polymer. 8The designation is used for reference to the polymer fraction that isinsoluble in alcohol and acetone.

can be eliected by the action of air or oxygen. Where the polymer is tobe used in sealing, caulking, or in the Polymer IV, the linear polymerprepared by the reacfabrication of solid parts, the choice of oxidizingagent tion of sodium tetrathiocarbonate with dichloroethyl will begoverned to some extent by the end use, an formal, was a light greensolid with the consistency of oxidizing agent preferably being selectedwhich can reputty. It gradually softened on heating and became quitemain in the final product. 75 fluid at -l00 C. It was soluble in anilineand in dimethyl formamide. Its sulfar content was found to be 35.4%.

The infrared absorption spectrum of Polymer IV has characteristicabsorption peaks at 3.4 to 3.5 microns, 6.8 microns, 7.1 microns, 7.3microns, 7.9 microns, 8.3 microns, 8.7 microns, 8.8 microns, 9.1microns, 9.3 microns, 10.2 microns, and 12.1 microns.

A polymer prepared in the same manner as Polymer IV above except thatdibromoethyl formal was substituted for dichloroethyl formal had similarcharacteristics and a substantially identical infrared spectrum.

Polymer V, the cross linked polymer prepared by the reaction of sodiumtetrathiocarbonate with dichloroethyl formal and trichloropropane (1.00:0.925:0.05 mole EXAMPLE 4 Polymers were prepared from sodiumtetrathiocarbonate, dichloroethyl formal and trichloropropane in moleratios 1.020.99720002 (Polymer VI) and 1.0:0.985:0.010 (Polymer VII) bytwo different procedures.

In the first procedure, the monomers were added to cold ethanol and themixture was refluxed for 24 hours under nitrogen. In the secondprocedure a hot (75 C.) mixture of dichloroethyl formal andtrichloropropane was added over a 5-minute period to a refluxing slurryof sodium tetrathiocarbonate in ethanol and the resulting mixture wasrefluxed 24 hours under nitrogen. The yields and viscosities of thevarious fractions of polymers obratio), was a gray rubbery solid. Thepolymer softened tained by each method are shown in Table II below:

TABLE II.YIELDS AND PROPERTIES OF TETRATHIOCARBONATE POLYMERS PREPAREDWITH DIFFERENT AMOUNTS OF TRICI-ILOROPROPANE Yield of Polymer Fractions,Sulfur Mole percent 1 Total Viscosity of Polymer Fractions content oftriehlo- Procey l of insoluble Polymer number roprodule Insolublepolymer, polymer pane number Alcohol Acetone alcohol, percent 1 AlcoholAcetone Insoluble fraction, soluble soluble acetone, soluble solublepercent or water 1 15 50 90 Viscous oil. Viscous oil. Plastic solid 2 101O 7O 9 d0 d 1 20 30 95 2 10 20 85 1 Yields are calculated as percent oftheory for a disulfide polymer.

and lost its elasticity at 210-225 C., melted at 240 C. and decomposedat 260280 C. It was swollen by aniline, but not dissolved. It wassoluble in dimethyl formamide. Its sulfur content was found to be 32.1%.

EXAMPLE 2 Liquefaction of polymers Polymers IV and V from Example 1above were mixed with hot (80 C.) alcoholic sodium hydrosulfide (NaHS)in the proportion of about one part of polymer per ten parts of 5%alcoholic solution of hydrosulfide. Upon agitation of the mixtures forabout 3 0 minutes, Polymer IV became a free flowing liquid, Polymer Vbecame a plastic mass in which the original particles had lost theiridentity.

A sample of Polymer IV was liquefied by heating a suspension of a onegram sample in 10 ml. of an aqueous solution containing about 5% sodiumhydrosulfide and about 2% sodium sulfite resulting in a fluid polymer.Treatment of samples of Polymers IV and V with 10% aqueous sodiumhydroxide at 100 C. for 2 hours did not change the viscosities of thepolymers, and treatment of these polymers with aniline under similarconditions had only slight if any effect on their viscosities.

The infrared absorption curve for the liquid polymer obtained bytreating Polymer IV with sodium hydrosulfide exhibits characteristicabsorption peaks at 3.4 microns, 3.5 microns, 6.8 microns, 7.1 microns,7.3 microns, 7.7 microns, -8.7 microns, 9.0 microns, 9.1 microns, 9.3microns, and 1 0.2 microns.

EXAMPLE 3 Curing of liquefied polymers One hundred parts each of theliquid polymers obtained from Polymer IV above, were mixed with 30 partseach of a paste prepared from 50 parts of lead dioxide and 45 parts ofdibutyl phthalate plasticizer and 5 parts of stearic acid, and a similarmixture was made from a commercial polysulfide polymer prepared by thereaction between sodium polysulfide of rank 2.25 and bis(2- chloroethyl)formal containing 1.5 trichloropropane, followed by liquefaction withsodium hydrosulfide and sodium sulfite. The mixtures were air cured for16 hours and resulted in the formation of rubbery products. When testedfor recovery from compression by a qualitative test, it was observedthat the curved polymers of the example were superior to the commercialproduct.

It will be noted that the two polymers prepared by the first procedure.Polymers VI-3 and VII-4, gave low yields of the insoluble fraction, andthe insoluble polymer from the preparation with the lower amount oftrichloropropane cross linking agent (Polymer VI3) was less viscous thanthe one from the preparation with more cross linking agent (PolymerVII-3 The two preparations by the second procedure (Polymers VI-4 andVII-4), yielded relatively high proportions of insoluble polymers, butthe viscosities of the insoluble fractions were not as high as those ofsimilar fractions from Example 1.

EXAMPLE 5 Preparation of disulfide monomer In ml. of ethanol there weremixed 13.7 grams (0.10 mole) of n-butyl bromide and 9.3 grams (0.05mole) of sodium tetrathiocarbonate and the resulting mixture wasrefluxed for 2 hours at 78 C.

The alcohol was evaporated from the mixture in a rotary evaporator, andthere was obtained a mixture of a salt and an oily liquid. The oilyliquid was extracted from the salt with petroleum ether, and recoveredfrom the extract by evaporation of the petroleum ether. The yellow oilremaining after evaporation of the solvent weighed 7.1 grams, had arefractive index of 1.4915, and it boiled at 94-95 C. at 4 mm. Hg.Elemental analysis of a distilled sample is shown below and compared tocalculated values for n butyl tetrathiocarbonate and for n-butyldisulfide.

These results indicate that the compound obtained was n-butyl disulfide.

obtained in a yield of 80% of theory.

While the above describe the preferred embodiments of my invention, itwill be understood that departures can 7 8 be made therefrom within thescope of the specification 2. The process according to claim 1 whereinthe reand claims. action medium is ethyl alcohol.

I claim: 3. The process according to claim 1 wherein not more 1. Theprocess for preparing a polymer characterized than about 0.10 mole ofthe dihaloethyl formal is reby the presence of the followingrepeating'units: 5 placed by trichloropropane.

References Cited which comprises heating a mixture of substantiallystoichiornetric proportions of an alkali metal tetrathiocar- UNITEDSTATES PATENTS bonate and a dihaloethyl formal wherein the halogen is 103 367 975 2/1968 Liggett a member selected from the group consisting ofchlorine a and bromine in a lower aliphatic alcohol reaction medium attemperatures between about 40 C. and about the DONALD E'CZAJAPnmaryExammer' reflux temperature of the reaction mixture for a period M, I,MARQUIS, Assistant Examiner, sutficient to produce a polymeric product.15

